Despite always having plenty of repair kits, being able to repair the companion only works about half the time, or in other words the ability to repair seems to be random. Sometimes you can repair and others the option is simply greyed out.
Playing on PC Win via GFN.
You can’t repair if it’s still got armor.(shield symbol by the bar) If it’s down to just health it can be repaired regularly.(+ sign by the bar). Hope this helps clear the inconsistent repairs. Although I think we should be able to repair armor if it’s not totally broken that’s not how it’s working right now.
You can’t repair if it’s still got armor.(shield symbol by the bar) If it’s down to just health it can be repaired regularly.(+ sign by the bar).
This took me some time to realize. They should have had some kind of popup saying “Can’t repair companion armor.”…but I guess that would break the immersion.
Although I think we should be able to repair armor if it’s not totally broken that’s not how it’s working right now.
This! 
I don’t know, maybe there’s a hint in the log.
But yes, that should have been more clear in the game.
I myself figured it out by trial and error if it is hinted at I missed it 
So when you can’t repair it is because the percentage shown is for the armor and not the companion? Good to know.
I was confused for the longest time…so I don’t think it’s hinted. Then I got the info about it in one of Tenebris videos now that I think about it. 
There are different icons that show if it still has armor or not.